1. Field of the Invention
The present invention relates to a dot matrix display apparatus. More specifically, the present invention relates to a dot matrix display apparatus for displaying a limited number of characters, wherein the characters are displayed such that the display position of each character is successively shifted from the right to the left, for example.
2. Description of the Prior Art
FIG. 1 is a view showing one example of a dot matrix display for explaining the background of the invention. Conventionally, a dot matrix display has been used which displays each character using dots arranged in m columns and n rows, where m and n are natural numbers, such as "4.times.7", "5.times.7", "7.times.9" and so on. In such dot matrix display, a plurality of display units each including dots in m columns by n rows are provided, so that one character is allotted and is displayed to and by one display unit. In the case where a sentence including a plurality of characters is to be displayed, the characters being displayed are moved or shifted for each predetermined time period from the right to the left, for example, on a character-by-character basis. However, since such conventional moving or shifting display involves movement or shifting of characters on a character-by-character basis, it is very difficult for a viewer to read the displayed information.
On the other hand, an electric light signboard for displaying a series of words such as a sentence has also been well-known. In such an electric light signboard, the display region is not divided into characters but is rather used as a unitary region having dots in l columns and n rows, where l&gt;m, and characters are displayed such that the displayed positions of the characters are moved from the right to the left, for example, on a column-by-column basis. Such display may be referred to as "a scroll display". Since a scroll display makes the characters appear to flow, it is very easy for a viewer to read the characters. However, a display such as a conventional electric light signboard involves a problem. More specifically, with such conventional electric light signboard, generally a paper tape punch to represent a display signal associated with the characters being displayed needs to be prepared. The information contained in such punched paper tape is subjected to an optical reader so that the information is converted into an electrical display signal and the electrical display signal is loaded in a shift register, whereupon the display is driven in accordance with the content in the shift register. However, such display using a punched paper tape and an optical reader suffers from a tiresome maintenance of an optical reader and tiresome punching of a paper tape to provide information being displayed. Furthermore, it is extremely difficult to utilize the same paper tape for display of a different sentence. A scroll display type dot matrix display apparatus having easily legible displayed characters and of simple structure and maintenance have not been so far available.